Manufacture of hollow metal rods, bars, and the like



Patented May 6, 1930 UNITED- STATES ROBERT ABBOTT HADFIELD, OI WESTMINSTER, ENG-LAND MANUFACTURE OF HOLLOW METAL RODS, BARS, AND THE LIKE No Drawing. Application filed January 24, 1929, Serial No. 334,850, and in Great Britain July 7, 1927.

. This invention relates to improvements in the manufacture of hollow metal rods, bars and the like, hereinafter referred to generically as hollow metal rods, and particularly to the manufacture ofhollow steel rods for use asdrills.

The invention relates more particularly to that method of forming hollow metal rods accordingto which a billet, bloom or ingot of the metal of which'the hollow rod is to be made, is formed with acentral longitudinal hole that is filledwith ametal core after which the billet, bloom or ingot (hereinafter referred to as a billet) with core is worked, as by rolling or forging, into a solid compound rod of the desired length and cross section and the core then extracted to leave the re quired hollow rod.

It has been proposed to use for the core, a rod formed of metal of low elasticity but of adequate tensile strength to permit of, its being withdrawn from the hollow metal rod produced by rolling or forging the metal billet. Thus, it has been proposed to use as a core, a copper rod which, after the billet, with such a core, has been worked to form a compound rod of the required length and cross section, is removed byvdrawi'ng it from the surrounding rod by mechanical means, after first fracturing the ends of the rod to enable the extremity of the copper core to be seized and drawn out. In practice it is found that the copper core is liable, during its withdrawal, to break within the hollow rod and the withdrawal of the portionof the core remaining within the rod is very difiiculty to effect. To obviate this difficulty, it has been proposed to make the core in two lengths and to withdraw each length separately from the corresponding end of the hollow rod, but this mode of procedure is also found unsatisfactory as the two lengths of core are liable to become separated during the rolling or forging operation and result in the formation of an imperfect hollow rod. To overcome this disadvantage, it has been proposed to use a core that is weakened at a part thereof between its ends, as by nicking, sawing or boring and inserting in the nick, sawgate, hole or boring, a metal filling, so that after the billet with such a weakened core has been worked into a compound rod of the desired length and cross sectiomthecore, when it is subjectedto the tensile strain necessary for its withdrawal, will break and part into two portions which can be extracted separately at the ends of the hollow rod. It has also been proposed to use as the core, a rod of iron or steel, or of an iron, nickel, chromium steel alloy of such character that when stretched, it will elongate substantially uniformly along its entire length without local constriction until sulficiently reduced in diameter to enable it to be withdrawn as a whole from the fin-. ished rod. The present invention has for its object to enable hollow metal rods to be produced according to the general method hereinbefore referred to, with a smooth inner surface, in a better and cheaper manner than heretofore.

For this purpose, in the manufacture of a hollow rod from a metal billet formed with a longitudinal hole therethrough as heretofore, it has been found by experiment, that a core of manganese steel of the kind commonly known as Hadfield manganese steel, gives very satisfactory results. Such steel, as is well known, contains say from about 0.75% to 1.5% and above of carbon and from about- 9% to 15% or more of manganese, usually 30 about 1% of carbon and about 11 to 13% of manganese. Such steel has considerable tensile strength and great ductility whereby it can be elongated by tensile force and simultaneously reduced in cross-section along its length until it finally breaks under the action of the tensile force.

lhe present invention consists therefore in using in the manufacture of a hollow rod as herein set forth, a core of manganese steel of the kind referred to.

In carrying out the invention, abillet, or blank (hereinafter called for brevitya bi-llet) formed of the metal of which the desired hollow metal rod is to be formed, is provided with a rod or core of ordinary rolled manganese steel of the kind referred to, preferably in the form of an ordinary rolled untoughened rod of such steel, and the billet, with the said core, is then heated and worked,

as in the ordinary way, by rolling, forging or drawing, to reduce it to thedesired length and cross-section, after which the ends of the resulting outer rod'are nicked and fractured, and the core subjected to sufficient tensile force, as by gripping devices applied to its two ends and connected to pulling mecha' nism, as to cause it to become increased in length sufficiently to enable it to be readily withdrawn from the hollow rod. j

In carrying out the invention,- the elongation of-.the manganese steel core may conveniently be continued until the core owing to its "considerable reduction in cross-sectional area, breaks whilst within the outer rod, thus facilitating its rapid withdrawal from the rod. The core, beforebeing placed in or surrounded by the billet, may, as with cores of other metal, be coated, with a layer or material, as for instance black lead, graphite 'or the like, that is not affected by heat and which willact to preventdir'ect contact between the core and billet durin working of the billet and core, and will a terwards facilitate the removal of the worked core from the worked rod. A hollow rod made as described has a very smooth inner surface and. may be of circular, polygonal or other section externally, as well understood.

The invention canadvantageouslybe ap-' plied in connection with the manufacture of hollow steel rods, such as carbon steel rods,

. to be used as drills, but may be applied" in connection with the manufacture of hollow rods of iron or of other metal for various uses. It may also be applied in connection with the manufacture of hollow rods made of metallic alloys, hereinafter included in the term metal rods, used in the appended claims. It may also be applied in connection with the manufacture of rods having two or more parallel holes therein, forming a double or multiplebore tube, suitable for instance in the manufacture of multiple bore rifles and revolvers', using for the purpose, a billet having two or more holes therein filled with two or more cores of manganese steel of the kind referred to.

Manganese steel of the kind hereinbefore referred to, suitable for carrying out the invention, may in some cases, and as is well known, contain apreciable amounts of other elements, as for instance silicon, chromium,

or aluminium, or two or more of such elements, and such manganese steel 1s to be understood as includedln the general term, manganese steel, used in the appended claims.

By the use of cores formed of manganese steel of the kind hereinbefore described, hollow metal rods having smooth internal surfaces can readily, be made in an economical manner, such steel cores being much cheaper than the cores of copper, or of other ferrous alloys heretofore used.

Whatl claim is 1, In the manufacture of a hollow metal rod by working a billetprovided with a metal -core into a solid compound rod of the delength andcross-section an'd subjecting the core to sufiicient tensile force-to cause it to become increased in length and reduced in cross-section throughout its length to a sulficombined billet and core to the. required eient extent to enable it to be readily removed from the outer hollow rod.

3. The manufacture of a hollow metal rod consisting in providinga billet formed of the metal of which the desired hollow rod is to be made with a core formed of a rolled rod of untoughened manganese steel of thekind .herein referred to, working the combined billet and core to the required length and cross section and. subjecting the core to suflicient tensile force to cause 1t to become 1ncreased in length and reduced in cross section throughout its length to a suliicient extent to enable it to be readily removed from the outer hollow rod. Y

4. The manufacture of a hollow metal rod consisting in providing a billet formed of the metal of which the desired hollow rod is to be made with a core of manganese'steel of the kind herein referred to, working the combined billet and core to the required length and cross-section and subjecting the core to sufficient tensile force to cause it to become increased in length and reduced in cross section throughout its length until it becomes fractured within the resulting outer rod and withdrawing the divided portions of the core from said rod.

5. Themanufacture of a hollow steelrod,

suitable for use as a drill, by providing a billet formed of steel of the required quality, with a core of manganese steel of the kind hereinbefore referred to, working the combined billet and core to the required length and cross-section and subjecting the core to smficient tensile force to cause it to become increased in length and simultaneously reduced in cross-section to such an extent as to admit of its ready removal from the result ing hollow steel rod. I

' 6. The herein-described method'of manufacturing a hollow metal rod, said method consisting in providing a billet formed of the metal of which the hollow rod is to be made, with a rolled rod of untoughened manganese steel of the kind herein referred to, working 'the comb'inedbillet and core to the desired said core to suflicient tensile force to cause it first-to become increased in length and reduced in cross-section to such an extent that it becomes freed from the outer resulting hollowrod and then to become fractured within the said rod and then removing the divided portions of the core from said hollow rod.

7. 'In the art of manufacturing a hollow metal rod which consists in heating a metal billet provided with a metal core to a working temperature, working the combined billet and core into a solid compound rod of the desired length and cross section and afterwards subjecting the core to tension to ing crease its length and reduce it in diameter to enable it to be removed from the outer rod, using as the core material, a core of manganese steel of the kind herein referred to. v 8. The manufacture of a hollow metal rod consisting in providing a hollow billet formed of the metal of which the desired hollow rod is to be made, with a core of manganese steel of the kind referred to, heating the compound billet and core to a rolling temperature,

working the combined billet and core to the required length and cross section by rolling, cooling the resulting compound rod and core, and subjecting the core to suflicient tensile force to cause it to become increased in length and reduced in cross section throughout its length to a suflicient extent to enable it to be removed from the outer hollow rod.

Signed at London, England, this fourteenth day of December, 1928. ROBERT ABBOTT HADFIELD. 

